Method for prolonging optical fiber transmission distance based on maximum merging ratio

Abstract

The invention belongs to the technical field of optical fiber communication, and particularly relates to a method for prolonging an optical fiber transmission distance based on a maximum merging ratio. And resampling the digital baseband signal, loading the digital baseband signal to a waveform generator, and converting the digital baseband signal into two paths of electric signals for driving an IQ modulator to modulate two groups of optical carriers. An IQ signal is divided into two paths of orthogonal single polarization signals through a polarization beam splitter, and the two paths of orthogonal single polarization signals pass through a section of polarization maintaining optical fiber and are combined into an orthogonal polarization multiplexing signal through a polarization beam combiner. And then the polarization multiplexing signal is coupled into an optical fiber for long-distance transmission, and an optical amplifier is used for relaying. Coherent detection is carried out on the optical signal after polarization demultiplexing, and a generated baseband electric signal is captured; and finally, carrying out dispersion compensation and balanced digital signal processing on the sampled signals, and combining the two paths of signals by using a maximum combination ratio algorithm so as to improve the signal-to-noise ratio. The anti-noise performance of the signal after long-distance optical fiber transmission is improved, the signal-to-noise ratio of the recovered signal is improved, and long-distance optical fiber transmission is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber communication, and in particular relates to a method for extending optical fiber transmission distance based on a maximum combining ratio. Background Art

[0002] As disruptive technologies such as the Internet of Things (IoT) and Artificial Intelligence (AI) bring us into an era of unprecedented connectivity and data generation, current communication systems face severe challenges in increasing transmission rates and transmission distances. They show excellent data throughput and signal stability in long-distance transmission. Coherent optical communication systems have proven to be very suitable for long-distance, high-capacity transmission. By using repeaters, signals can be amplified to meet the standards for long-distance transmission. However, this also causes signal attenuation, reduces the number of repeaters used, reduces system costs, and improves system reliability. The distance to the repeater is the main factor affecting the transmission distance. The scattering and absorption of optical fibers cause signal loss, and the dispersion characteristics of optical fibers cause changes in pulse bandwidth, reducing the quality of signal transmission. Physical factors such as polarization mode dispersion, group velocity dispersion, and optical filtering are still limiting factors, which seriously affect the transmission distance of communication lines. Therefore, it has become extremely necessary to explore new long-distance coherent optical fiber transmission architectures. Summary of the invention

[0003] The object of the present invention is to provide a method for extending the optical fiber transmission distance based on the maximum combining ratio with fast communication speed and high reliability, which is applicable to the optical fiber coherent transmission system architecture of various optical fibers and modulation formats.

[0004] The method for extending the optical fiber transmission distance based on the maximum combining ratio provided by the present invention comprises the following specific steps:

[0005] (1) After resampling, the original QAM signal is loaded into an arbitrary waveform generator and converted into two electrical signals: I and Q. The two electrical signals I and Q drive the IQ modulator to generate a vector optical signal.

[0006] (2) The vector optical signal is split into two orthogonal single polarization signals by a polarization beam splitter, passed through a section of polarization-maintaining fiber, and then combined into an orthogonal polarization multiplexed signal by a polarization beam combiner;

[0007] (3) The orthogonal polarization multiplexed signals are coupled into the transmission optical fiber for long-distance transmission, and an optical amplifier is used for relaying during the transmission process; after reaching the receiving end, the transmitted signals are polarization demultiplexed, and the polarization demultiplexed signals are coherently detected, converted into baseband electrical signals through optical-electrical signals, and the generated baseband electrical signals are captured;

[0008] (4) The baseband electrical signal passes through the DSP at the receiving end to obtain two QAM signals. The two QAM signals are combined using the maximum combining ratio algorithm to obtain the original QAM signal after transmission.

[0009] In the present invention, the bit error rate and signal-to-noise ratio of the original QAM signal after transmission are calculated to evaluate the transmission performance of the entire scheme. The original signal quality is basically maintained, and the signal-to-noise ratio is improved by 2.3dB compared with the traditional transmission scheme. The constellation diagram has obvious convergence and the signal quality is significantly improved.

[0010] In the present invention, the transmission optical fiber is one of various optical fibers such as compatible single-mode optical fiber, multi-mode optical fiber, multi-mode multi-core optical fiber, etc.

[0011] In the present invention, the orthogonal polarization multiplexing signal transmits the same vector optical signal in two orthogonal polarization directions.

[0012] In the present invention, in the optical fiber transmission system, the polarization multiplexing signal completes the electrical-optical conversion in the IQ modulator, and beats with another optical signal in the photodetector (PD) to generate a coherent signal.

[0013] In the present invention, the original QAM signal includes a probability shaped QAM signal.

[0014] Compared with the prior art, the present invention utilizes polarization multiplexing technology to transmit the same signal in two orthogonal polarization directions, and realizes the integration of the two signals through a maximum combining ratio algorithm.

[0015] The present invention improves the noise resistance of signals after long-distance optical fiber transmission, improves the signal-to-noise ratio of the restored signal, and realizes long-distance optical fiber transmission. The transmission architecture is compatible with flexible modulation formats and multiple optical fiber types, and can adjust the multiplexing technology according to transmission requirements to complete high-speed long-distance transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram of the architecture of the optical fiber coherent transmission system based on polarization multiplexing technology and maximum combining ratio algorithm proposed in the present invention.

[0017] Figure 2 Evaluation results of bit error rate and signal-to-noise ratio of the combined QAM signal. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0019] The method for extending the optical fiber transmission distance based on the maximum combining ratio of the present invention comprises the following steps:

[0020] 1) Generate QAM signal offline, resample it, load it into arbitrary waveform generator, and convert it into two electrical signals;

[0021] 2) The two electrical signals are divided into I and Q to drive the IQ modulator to generate a vector optical signal;

[0022] 3) Transmitting the vector optical signal into the polarization multiplexing module; wherein the vector optical signal is split into two orthogonal single polarization signals by a polarization beam splitter, passes through a section of polarization-maintaining optical fiber, and is combined into an orthogonal polarization multiplexed signal by a polarization beam combiner;

[0023] 4) Coupling the orthogonal polarization multiplexing signal into the optical fiber for long-distance transmission and using an optical amplifier for relaying;

[0024] 5) Polarization demultiplexing the transmission signal through a polarization demultiplexing module;

[0025] 6) Perform coherent detection on the optical signal after polarization demultiplexing and perform photoelectric signal conversion;

[0026] 7) Capture the generated baseband electrical signal;

[0027] 8) The received signal passes through the receiving end DSP to obtain two-way QAM signals;

[0028] 9) Combine the two signals using the maximum combining ratio algorithm.

[0029] The working process is as follows: after the original QAM signal is resampled, it is loaded into an arbitrary waveform generator and converted into two electrical signals, I and Q. These two signals drive the IQ modulator to generate a vector optical signal; this vector optical signal is divided into two orthogonal polarization directions in the polarization multiplexing module through a polarization beam splitter to transmit the same vector optical signal, and the transmission signals are the same, and there is no rigid requirement for the delay device. After being transmitted through polarization-maintaining optical fiber, it is combined into an orthogonal polarization multiplexing signal through a polarization combiner; then, the orthogonal polarization multiplexing signal is coupled into the optical fiber for long-distance transmission, and an optical amplifier is used for relaying during the transmission process. After reaching the receiving end, the transmission signal is polarization demultiplexed, and the demultiplexed optical signal is coherently detected to realize the optical-electrical signal conversion and capture the generated baseband electrical signal. The received signal is processed by the receiving end DSP to obtain the two QAM signals carried. Then, the two signals are combined using the maximum combining ratio algorithm.

[0030] Final evaluation: Calculate the bit error rate and signal-to-noise ratio of the combined QAM signal to evaluate the performance of the solution; the evaluation results are as follows: Figure 2 As shown in the figure, it basically maintains the original signal quality, and the signal-to-noise ratio is improved by 2.3dB compared with the traditional transmission scheme. The constellation diagram has obvious convergence and the signal quality is significantly improved.

[0031] The transmission optical fiber can be one of a variety of optical fibers such as compatible single-mode optical fiber, multi-mode optical fiber, multi-mode multi-core optical fiber, etc.

[0032] In the optical fiber transmission system, the orthogonal polarization multiplexing signal completes the electrical-optical conversion in the IQ modulator, and beats with another optical signal in the photodetector (PD) to generate a coherent signal.

[0033] The original QAM signal includes a probability shaped QAM signal.

[0034] This solution is applicable to a variety of optical fiber communication systems and has good universality.

[0035] For example, in a single-mode fiber coherent transmission system, the electrical signal completes the electrical-optical conversion in the I / Q modulator, and the IQ signal is divided into two orthogonal single polarization signals through a polarization beam splitter, and then passes through a section of polarization-maintaining fiber, and is combined into a polarization multiplexing signal through a polarization beam combiner, and then transmitted through the fiber, and relayed using an optical amplifier; after passing through the polarization beam splitter and coherently received in the coherent receiver, the sampled data is sampled, and the sampled data is subjected to the receiving end digital signal processing and the maximum combining ratio algorithm. Among them, the core algorithm, the maximum combining ratio algorithm, is used to combine the two equalized signals based on the maximum combining ratio principle, and its operation expression is shown in formula (1):

[0036] y MRC =w H y

[0037]

[0038] Formula (1) is the function expression of the maximum merging ratio algorithm;

[0039] In formula (1), w is the weight factor vector, y MRC is the output signal after the maximum merging ratio algorithm is combined, (·) H represents the transposed conjugate, y represents the input signal of the maximum merging ratio algorithm, and h i It is the diagonal element of the transmission matrix. Since the transmitted data is the same, the transmission matrix can be combined into a diagonal matrix, whose diagonal elements can cover all the degradation effects of the channel on the transmission signal during the optical fiber transmission process. T represents transpose, and n represents the diagonal element h of the transmission matrix. i The original transmitted symbols are restored through the maximum combining ratio algorithm to evaluate the performance improvement of the system.

[0040] Compared with the prior art, the present invention improves the signal-to-noise ratio of QAM signals and realizes long-distance optical fiber transmission. The transmission architecture is compatible with flexible modulation formats and multiple optical fiber types, and can adjust the multiplexing technology according to transmission requirements. The present invention realizes high-speed long-distance transmission and provides a good solution for future optical fiber transmission.

[0041] Compared with the related art, the method for extending the optical fiber transmission distance based on the maximum combining ratio provided by the present invention has the following beneficial effects:

[0042] The present invention provides a dual-polarization maximum combining ratio optical fiber coherent transmission system method. Compared with the prior art, the implementation method uses polarization multiplexing technology to transmit the same signal in two orthogonal polarization directions, and realizes the integration of two signals through the maximum combining ratio algorithm. This solution improves the noise resistance of the signal after long-distance optical fiber transmission, improves the signal-to-noise ratio of the restored signal, and realizes long-distance optical fiber transmission. This transmission architecture is compatible with flexible modulation formats and multiple optical fiber types, and can adjust the multiplexing technology according to transmission requirements to complete high-speed long-distance transmission.

[0043] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for extending optical fiber transmission distance based on maximum combining ratio, characterized in that: The specific steps are as follows: (1) After resampling, the original QAM signal is loaded into an arbitrary waveform generator and converted into two electrical signals: I and Q. The two electrical signals I and Q drive the IQ modulator to generate a vector optical signal. (2) The vector optical signal is split into two orthogonal single polarization signals by a polarization beam splitter, passed through a section of polarization-maintaining fiber, and then combined into an orthogonal polarization multiplexed signal by a polarization beam combiner; (3) The orthogonal polarization multiplexed signals are coupled into the transmission optical fiber for long-distance transmission, and optical amplifiers are used for relaying during the transmission process; after reaching the receiving end, the transmitted signals are polarization demultiplexed, and the polarization demultiplexed signals are coherently detected, converted into baseband electrical signals through optoelectronic signals, and the generated baseband electrical signals are captured; (4) The baseband electrical signal passes through the DSP at the receiving end to obtain two QAM signals. The two QAM signals are combined using the maximum combining ratio algorithm to obtain the original QAM signal after transmission.

2. The method for extending optical fiber transmission distance based on maximum combining ratio according to claim 1, characterized in that: The transmission optical fiber is one of various optical fibers such as compatible single-mode optical fiber, multi-mode optical fiber, multi-mode multi-core optical fiber, etc.

3. The method for extending optical fiber transmission distance based on maximum combining ratio according to claim 1, characterized in that: The orthogonal polarization multiplexing signal transmits the same vector optical signal in two orthogonal polarization directions.

4. The method for extending optical fiber transmission distance based on maximum combining ratio according to claim 1, characterized in that: In the optical fiber transmission system, the polarization multiplexing signal completes the electrical-optical conversion in the IQ modulator, and beats with another optical signal in the photoelectric detector PD to generate a coherent signal.

5. The method for extending optical fiber transmission distance based on maximum combining ratio according to claim 1, characterized in that: The original QAM signal is a probability shaped QAM signal.

Images